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607ca46e DH |
1 | #ifndef _UAPI_LINUX_VIRTIO_RING_H |
2 | #define _UAPI_LINUX_VIRTIO_RING_H | |
ecda85e7 JG |
3 | /* An interface for efficient virtio implementation, currently for use by KVM, |
4 | * but hopefully others soon. Do NOT change this since it will | |
607ca46e DH |
5 | * break existing servers and clients. |
6 | * | |
7 | * This header is BSD licensed so anyone can use the definitions to implement | |
8 | * compatible drivers/servers. | |
9 | * | |
10 | * Redistribution and use in source and binary forms, with or without | |
11 | * modification, are permitted provided that the following conditions | |
12 | * are met: | |
13 | * 1. Redistributions of source code must retain the above copyright | |
14 | * notice, this list of conditions and the following disclaimer. | |
15 | * 2. Redistributions in binary form must reproduce the above copyright | |
16 | * notice, this list of conditions and the following disclaimer in the | |
17 | * documentation and/or other materials provided with the distribution. | |
18 | * 3. Neither the name of IBM nor the names of its contributors | |
19 | * may be used to endorse or promote products derived from this software | |
20 | * without specific prior written permission. | |
21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND | |
22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
24 | * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE | |
25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
31 | * SUCH DAMAGE. | |
32 | * | |
33 | * Copyright Rusty Russell IBM Corporation 2007. */ | |
d768f32a TH |
34 | #ifndef __KERNEL__ |
35 | #include <stdint.h> | |
36 | #endif | |
607ca46e | 37 | #include <linux/types.h> |
eef960a0 | 38 | #include <linux/virtio_types.h> |
607ca46e DH |
39 | |
40 | /* This marks a buffer as continuing via the next field. */ | |
41 | #define VRING_DESC_F_NEXT 1 | |
42 | /* This marks a buffer as write-only (otherwise read-only). */ | |
43 | #define VRING_DESC_F_WRITE 2 | |
44 | /* This means the buffer contains a list of buffer descriptors. */ | |
45 | #define VRING_DESC_F_INDIRECT 4 | |
46 | ||
89a9157e TB |
47 | /* |
48 | * Mark a descriptor as available or used in packed ring. | |
49 | * Notice: they are defined as shifts instead of shifted values. | |
50 | */ | |
51 | #define VRING_PACKED_DESC_F_AVAIL 7 | |
52 | #define VRING_PACKED_DESC_F_USED 15 | |
53 | ||
607ca46e DH |
54 | /* The Host uses this in used->flags to advise the Guest: don't kick me when |
55 | * you add a buffer. It's unreliable, so it's simply an optimization. Guest | |
56 | * will still kick if it's out of buffers. */ | |
57 | #define VRING_USED_F_NO_NOTIFY 1 | |
58 | /* The Guest uses this in avail->flags to advise the Host: don't interrupt me | |
59 | * when you consume a buffer. It's unreliable, so it's simply an | |
60 | * optimization. */ | |
61 | #define VRING_AVAIL_F_NO_INTERRUPT 1 | |
62 | ||
89a9157e TB |
63 | /* Enable events in packed ring. */ |
64 | #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 | |
65 | /* Disable events in packed ring. */ | |
66 | #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 | |
67 | /* | |
68 | * Enable events for a specific descriptor in packed ring. | |
69 | * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). | |
70 | * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. | |
71 | */ | |
72 | #define VRING_PACKED_EVENT_FLAG_DESC 0x2 | |
73 | ||
74 | /* | |
75 | * Wrap counter bit shift in event suppression structure | |
76 | * of packed ring. | |
77 | */ | |
78 | #define VRING_PACKED_EVENT_F_WRAP_CTR 15 | |
79 | ||
607ca46e DH |
80 | /* We support indirect buffer descriptors */ |
81 | #define VIRTIO_RING_F_INDIRECT_DESC 28 | |
82 | ||
83 | /* The Guest publishes the used index for which it expects an interrupt | |
84 | * at the end of the avail ring. Host should ignore the avail->flags field. */ | |
85 | /* The Host publishes the avail index for which it expects a kick | |
86 | * at the end of the used ring. Guest should ignore the used->flags field. */ | |
87 | #define VIRTIO_RING_F_EVENT_IDX 29 | |
88 | ||
a865e420 MT |
89 | /* Alignment requirements for vring elements. |
90 | * When using pre-virtio 1.0 layout, these fall out naturally. | |
91 | */ | |
92 | #define VRING_AVAIL_ALIGN_SIZE 2 | |
93 | #define VRING_USED_ALIGN_SIZE 4 | |
94 | #define VRING_DESC_ALIGN_SIZE 16 | |
95 | ||
5c669c4a RC |
96 | /** |
97 | * struct vring_desc - Virtio ring descriptors, | |
98 | * 16 bytes long. These can chain together via @next. | |
99 | * | |
100 | * @addr: buffer address (guest-physical) | |
101 | * @len: buffer length | |
102 | * @flags: descriptor flags | |
103 | * @next: index of the next descriptor in the chain, | |
104 | * if the VRING_DESC_F_NEXT flag is set. We chain unused | |
105 | * descriptors via this, too. | |
106 | */ | |
607ca46e | 107 | struct vring_desc { |
eef960a0 | 108 | __virtio64 addr; |
eef960a0 | 109 | __virtio32 len; |
eef960a0 | 110 | __virtio16 flags; |
eef960a0 | 111 | __virtio16 next; |
607ca46e DH |
112 | }; |
113 | ||
114 | struct vring_avail { | |
eef960a0 MT |
115 | __virtio16 flags; |
116 | __virtio16 idx; | |
117 | __virtio16 ring[]; | |
607ca46e DH |
118 | }; |
119 | ||
120 | /* u32 is used here for ids for padding reasons. */ | |
121 | struct vring_used_elem { | |
122 | /* Index of start of used descriptor chain. */ | |
eef960a0 | 123 | __virtio32 id; |
607ca46e | 124 | /* Total length of the descriptor chain which was used (written to) */ |
eef960a0 | 125 | __virtio32 len; |
607ca46e DH |
126 | }; |
127 | ||
a865e420 MT |
128 | typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE))) |
129 | vring_used_elem_t; | |
130 | ||
607ca46e | 131 | struct vring_used { |
eef960a0 MT |
132 | __virtio16 flags; |
133 | __virtio16 idx; | |
a865e420 | 134 | vring_used_elem_t ring[]; |
607ca46e DH |
135 | }; |
136 | ||
a865e420 MT |
137 | /* |
138 | * The ring element addresses are passed between components with different | |
139 | * alignments assumptions. Thus, we might need to decrease the compiler-selected | |
140 | * alignment, and so must use a typedef to make sure the aligned attribute | |
141 | * actually takes hold: | |
142 | * | |
143 | * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes | |
144 | * | |
145 | * When used on a struct, or struct member, the aligned attribute can only | |
146 | * increase the alignment; in order to decrease it, the packed attribute must | |
147 | * be specified as well. When used as part of a typedef, the aligned attribute | |
148 | * can both increase and decrease alignment, and specifying the packed | |
149 | * attribute generates a warning. | |
150 | */ | |
151 | typedef struct vring_desc __attribute__((aligned(VRING_DESC_ALIGN_SIZE))) | |
152 | vring_desc_t; | |
153 | typedef struct vring_avail __attribute__((aligned(VRING_AVAIL_ALIGN_SIZE))) | |
154 | vring_avail_t; | |
155 | typedef struct vring_used __attribute__((aligned(VRING_USED_ALIGN_SIZE))) | |
156 | vring_used_t; | |
157 | ||
607ca46e DH |
158 | struct vring { |
159 | unsigned int num; | |
160 | ||
a865e420 | 161 | vring_desc_t *desc; |
607ca46e | 162 | |
a865e420 | 163 | vring_avail_t *avail; |
607ca46e | 164 | |
a865e420 | 165 | vring_used_t *used; |
607ca46e DH |
166 | }; |
167 | ||
e7c8cc35 MG |
168 | #ifndef VIRTIO_RING_NO_LEGACY |
169 | ||
607ca46e DH |
170 | /* The standard layout for the ring is a continuous chunk of memory which looks |
171 | * like this. We assume num is a power of 2. | |
172 | * | |
173 | * struct vring | |
174 | * { | |
175 | * // The actual descriptors (16 bytes each) | |
176 | * struct vring_desc desc[num]; | |
177 | * | |
178 | * // A ring of available descriptor heads with free-running index. | |
eef960a0 MT |
179 | * __virtio16 avail_flags; |
180 | * __virtio16 avail_idx; | |
181 | * __virtio16 available[num]; | |
182 | * __virtio16 used_event_idx; | |
607ca46e DH |
183 | * |
184 | * // Padding to the next align boundary. | |
185 | * char pad[]; | |
186 | * | |
187 | * // A ring of used descriptor heads with free-running index. | |
eef960a0 MT |
188 | * __virtio16 used_flags; |
189 | * __virtio16 used_idx; | |
607ca46e | 190 | * struct vring_used_elem used[num]; |
eef960a0 | 191 | * __virtio16 avail_event_idx; |
607ca46e DH |
192 | * }; |
193 | */ | |
194 | /* We publish the used event index at the end of the available ring, and vice | |
195 | * versa. They are at the end for backwards compatibility. */ | |
196 | #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) | |
eef960a0 | 197 | #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) |
607ca46e DH |
198 | |
199 | static inline void vring_init(struct vring *vr, unsigned int num, void *p, | |
200 | unsigned long align) | |
201 | { | |
202 | vr->num = num; | |
203 | vr->desc = p; | |
d6547f2a | 204 | vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc)); |
d768f32a | 205 | vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) |
607ca46e DH |
206 | + align-1) & ~(align - 1)); |
207 | } | |
208 | ||
209 | static inline unsigned vring_size(unsigned int num, unsigned long align) | |
210 | { | |
eef960a0 | 211 | return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) |
607ca46e | 212 | + align - 1) & ~(align - 1)) |
eef960a0 | 213 | + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; |
607ca46e DH |
214 | } |
215 | ||
e7c8cc35 MG |
216 | #endif /* VIRTIO_RING_NO_LEGACY */ |
217 | ||
607ca46e | 218 | /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ |
e412d3a3 | 219 | /* Assuming a given event_idx value from the other side, if |
607ca46e DH |
220 | * we have just incremented index from old to new_idx, |
221 | * should we trigger an event? */ | |
222 | static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) | |
223 | { | |
224 | /* Note: Xen has similar logic for notification hold-off | |
225 | * in include/xen/interface/io/ring.h with req_event and req_prod | |
226 | * corresponding to event_idx + 1 and new_idx respectively. | |
227 | * Note also that req_event and req_prod in Xen start at 1, | |
228 | * event indexes in virtio start at 0. */ | |
229 | return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); | |
230 | } | |
231 | ||
89a9157e TB |
232 | struct vring_packed_desc_event { |
233 | /* Descriptor Ring Change Event Offset/Wrap Counter. */ | |
234 | __le16 off_wrap; | |
235 | /* Descriptor Ring Change Event Flags. */ | |
236 | __le16 flags; | |
237 | }; | |
238 | ||
239 | struct vring_packed_desc { | |
240 | /* Buffer Address. */ | |
241 | __le64 addr; | |
242 | /* Buffer Length. */ | |
243 | __le32 len; | |
244 | /* Buffer ID. */ | |
245 | __le16 id; | |
246 | /* The flags depending on descriptor type. */ | |
247 | __le16 flags; | |
248 | }; | |
249 | ||
607ca46e | 250 | #endif /* _UAPI_LINUX_VIRTIO_RING_H */ |